1. Field of the Invention
The present invention relates to disparity value deriving devices, equipment control systems, movable apparatuses, and robots.
2. Description of the Related Art
In recent years, vehicle-mounted systems have generally been used for preventing automobile collisions by measuring the distance between automobiles or the distance between an automobile and an obstacle. A stereo matching process using the principle of triangulation using a stereo camera has been used as a method of measuring the distance. The stereo matching process is a process of obtaining disparity by matching corresponding pixels between a reference image captured by one of two cameras of a stereo camera and a comparison image captured by the other camera, and calculating the distance between the stereo camera and an object included in the images from the disparity. The calculation of the distance to an object by this stereo matching process using a stereo camera enables a variety of recognition processing, and brake control and steering control for preventing collisions.
The stereo matching process as described above includes the block matching method in which, in order to evaluate the similarity between images, regions are cut out from the images to be compared and, for example, the sum of absolute differences (SAD) of luminance, the sum of squared differences (SSD), and the zero-mean normalized cross-correlation (ZNCC) are obtained for the regions. However, it is difficult to extract image features in a portion where texture indicating the amount of change in luminance of an object in an image is weak, and the block matching method may not provide accurate disparity. A technique is then proposed as a method for deriving precise disparity, in which not only the cost of a pixel in a comparison image for a corresponding reference pixel in a reference image but also the costs of pixels in the neighborhood of the pixel in the comparison image are aggregated to derive disparity for an object with weak texture (see Japanese Patent Application Laid-open No. 2012-181142).
The technique described in Japanese Patent Application Laid-open No. 2012-181142, however, uses much memory and increases the image processing load due to the stereo matching process because the value of aggregated costs is obtained for each of the pixels continuously arranged to form an image. It is therefore difficult to obtain a disparity image configured with disparity values real-time.
Therefore, there is a need to provide a disparity value deriving device, an equipment control system, a movable apparatus, and a robot that are capable of reducing the image processing load and reducing the time required for deriving disparity values.